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Flap-related complications associated with mechanical microkeratomes are fewer with femtosecond laser-created flaps, according to Perry S. Binder, MS, MD.
Irvine, CA-Flap-related complications associated with mechanical microkeratomes are fewer with femtosecond laser-created flaps, according to Perry S. Binder, MS, MD.
Comparing flaps created using both technologies, Dr. Binder said the mechanical microkeratome is associated with flap-thickness errors and suction breaks.
“(However), when comparing the total number of complications between the two types of microkeratomes, there is basically no difference,” said Dr. Binder, clinical professor of ophthalmology, Gavin Herbert Department of Ophthalmology, University of California Irvine.
A 2002 study that included 84,771 LASIK cases in which either the Hansatome microkeratome or Automated Corneal Shaper microkeratome (both from Bausch + Lomb) were used, found a complication rate of 0.302%. A 2008 study, which included 3,009 patients that underwent LASIK in which the flaps were created using 30- or 60-Hertz femtosecond lasers (IntraLase), found a complication rate of 0.299%.
“The difference is that the complications resulting from use of mechanical microkeratomes are more vision-threatening compared with femtosecond laser complications,” he said.
For example, a button hole is microkeratome-related; however, a button hole that develops with vertical gas breakthrough when using a femtosecond laser is surgeon-related.
Another surgeon-related complication when using the femtosecond laser is a flap tear, Dr. Binder said.
The newer microkeratomes are still associated with epithelial defects, but do not occur with the femtosecond laser. The success of flap creation with a mechanical microkeratome depends on blade sharpness and quality, he said, which reduces the thickness of the flap in the second eye.
With a femtosecond laser, there is no difference in the flap thickness between both eyes of a patient.
Thick flaps also occur with mechanical microkeratomes as the result of thicker corneas, high IOP, slow translation, and downward pressure exerted by the surgeon.
The expected range with a microkeratome blade can also exceed 5 standard deviations. If the attempted thickness is 130 µm, the actual thickness can range from 65 to 225 µm, Dr. Binder said.
“The uniformity of femtosecond laser flaps is relatively planar over a 6- to 8-mm optical zone, whereas with mechanical microkeratomes, the blade dives in deep and comes up thinner,” he said.
However a concern with the femtosecond laser is that a steep side-cut angle predisposes to circumferential striae, Dr. Binder said.
The cost per procedure is also increased, but there are fewer enhancements and improved patient acceptance.
Comparing the two technologies, Dr. Binder said that mechanical microkeratomes are a good technology, have financial advantages when a femtosecond laser is unavailable, can create excellent flap thickness and standard deviations. However, they are technology-dependent and affected by individual ocular parameters.
The same system components can create different flap dimensions in the same patient.
Femtosecond lasers allow flap measurement without lifting the flap because the software controls the flap characteristics.
Dr. Binder noted that surgeons are switching to femtosecond lasers.
“The reasons are predictability, improved acuity, fewer enhancements, significantly decreased flap complications, significantly improved thickness predictability, and patient acceptance,” he said. “Because we have femtosecond lasers to create flaps, LASIK is a safe procedure.”
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